Glyphosate Summary of Analytical Chemistry and Residue Data DP#: 383931

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

MEMORANDUM

Date 24-March-2011

Subject: Glyphosate. Section 3 Registration for Application of the Potassium Salt of 

Glyphosate to Roundup Ready®Field Corn. Summary of Analytical Chemistry

and Residue Data. 

PC Codes: 103613 and 417300 DP Barcode: D383931

Decision No.: 437140 Registration Nos.: 524-537; 524-549

Petition No.: 0F7741 Regulatory Action: Section 3

Risk Assessment Type: not applicable Case No.: 178

TXR No.: not applicable CAS No.: 70901-20-1

MRID No.: 47982201 40 CFR: 180.364

From: Tom Bloem, Chemist

Risk Assessment Branch 1; Health Effects Division (RAB1/HED; 7509P)

Through: George F. Kramer, Ph.D., Senior Chemist

RAB1/HED (7509P)

To: James Tompkins/Hope Johnson RM 25

Registration Division (RD; 7505P)

Monsanto indicated that they have developed a new Roundup Ready®trait for field corn which 

enables properly timed glyphosate (N-(phosphonomethyl)glycine) applications to provide tassel 

control; Monsanto indicated that tassel control is desired as this will allow the generation of 

specific cross pollinations without the use of traditional methods to control self pollination. This 

new Roundup Ready®trait will be used only in seed corn production and Monsanto termed the 

process Round Hybridization SystemTM (RHSTM). The generation of RHSTM seed corn involves 

slightly later application timings than those currently registered. 
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Executive Summary

Background: Glyphosate is a nonselective Group 9 herbicide which disrupts the synthesis of the 

aromatic amino acids tyrosine, tryptophan, and phenylalanine through inhibition of 5-

enolpyruvylshikimate-3-phosphate synthase (EPSPS). Glyphosate is currently registered for preand post-emergence application to a variety of fruit, vegetable, and field crops. Tolerances are 

currently established for residues of glyphosate in/on various plant commodities (including field 

corn) at 0.2-400 ppm (40 CFR §180.364(a)) and for the combined residues of glyphosate and Nacetyl-glyphosate (expressed as glyphosate) in/on field corn, soybean, aspirated grain fractions 

(AGF), and livestock commodities at 0.1-310 ppm. The Glyphosate Reregistration Eligibility

Decision (RED) document was issued September 1993. A Registration Review Scoping 

document was completed in 2009 (D362745, J. Langsdale et al., 3-Jun-2009). 

The petitioner proposed a Section 3 registration for application of glyphosate to field corn used in 

RHSTM seed corn production. The petitioner is also proposing a tolerance for residues of 

glyphosate only in/on field corn forage of 13 ppm (revisions to the currently-established field 

corn stover and grain tolerances are not requested). Tolerances for the combined residues of 

glyphosate and N-acetyl-glyphosate (expressed as glyphosate; see Attachment 1 for structures) 

in/on field corn forage, stover, and grain are currently established at 6.0 ppm, 100 ppm, and 5.0 

ppm, respectively (180.364(a)(2)). HED notes that the tolerance expression includes residues of 

N-acetyl-glyphosate due to the introduction the Optimum GAT field corn variety (see Nature 

of the Residue Section in the Executive Summary for a description of this variety).

Proposed Use: The petitioner submitted proposed supplemental labels for Roundup 

WeatherMAX®(EPA Reg. No. 524-537) and Roundup Power MAX®(Reg. No. 524-549); both 

of these products are soluble-concentrate (SC) formulations consisting of glyphosate as the 

potassium salt at 4.51 lb ae/gallon. The submitted supplemental labels indicate that the 

application scenarios are for use in research field trials and for seed production of corn hybrids 

using the RHSTM system. Table 3 is a summary of the proposed application scenarios. The 

proposed use directions are similar to that currently registered with the exception of the tassel 

control instructions (V8-V13); the maximum seasonal application rate is the same. HED 

requests that the supplemental labels be altered to indicate the following (a revised Section B is 

requested): (1) the minimum spray volume for ground and aerial application is >2 gallons per 

acre (GPA); (2) postemergent directions should indicate that they apply to field corn up to the V8 

crop stage and that a maximum of 2.3 lb ae/acre/season may be applied; and (3) preharvest 

interval (PHI) of 30 days for forage and 7 days for grain and stover.

Nature of the Residue – Primary Crops: Metabolism studies conducted with nontransgenic 

corn, cotton, soybeans, and wheat were previously submitted and reviewed. Based on these data, 

HED concluded that the residue of concern in nontransgenic plants is glyphosate (Memo, R. 

Perfetti, 19-Oct-1992; RED, R. Perfetti, 27-Oct-1992; Memo, R. Perfetti, 17-Mar-1994). 

Metabolism studies have also been submitted on glyphosate-tolerant canola (D242628, T. Bloem, 

30-Nov-1998) and glyphosate-tolerant field corn (Roundup Ready®field corn; D217539, G. 

Kramer, 14-Mar-1996). The glyphosate-tolerant canola and field corn were genetically modified 

to express the EPSPS gene derived from Agrobacterium sp. (strain CP4) which codes for an 

EPSPS protein that has reduced affinity for glyphosate as compared to the endogenous EPSPS 

protein. The glyphosate-tolerant canola and corn were also genetically engineered to express the 
Glyphosate Summary of Analytical Chemistry and Residue Data DP#: 383931

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oxireductase gene which converts glyphosate to the nonherbicidal AMPA (aminomethyl 

phosphonic acid). Metabolism in these varieties of transgenic canola and corn was essentially

the same as the nontransgenic plants. Therefore, it was concluded that the terminal residue to be 

regulated, in nontransgenic plants and transgenic field corn and canola modified to express the 

Agrobacterium sp. EPSPS and oxireductase genes, is glyphosate.

Subsequent to this decision, HED approved DuPont requests permitting the commercialization of 

Optimum GAT soybean and Optimum GAT field corn (D346713, T. Bloem, 12-Mar2008; D357880, T. Bloem, 29-Oct-2008; D361315, T. Bloem, 14-Jan-2010). Optimum

GAT soybean was engineered to express the gat4601 gene (derived from Bacillus 

licheniformis; soil bacterium) and Optimum GAT field corn was engineered to express the 

gat4621 gene (derived from Bacillus licheniformis; soil bacterium) and the zm-hra gene 

(modified version of maize acetolactate synthase (ALS) gene). The gat4601 and the gat4621 

genes confer tolerance to glyphosate via acetylation of the secondary amine group of glyphosate 

(results in formation of the nonherbicidal N-acetyl-glyphosate); the zm-hra gene in Optimum

GAT field corn, encodes for an ALS protein which is not sensitive to the ALS-inhibiting 

herbicides. As a result of the introduction of these seed lines, HED concluded that the residues 

of concern in plants for tolerance expression and risk assessment should change from glyphosate 

to the combined residues of glyphosate and N-acetyl-glyphosate (D346713, T. Bloem, 12-Mar2008). Subsequent to this decision, it was determined that only the tolerance expression for field 

corn and soybean would change from glyphosate to the combined residues of glyphosate and Nacetyl-glyphosate; the tolerance expression for all other crops would remain as glyphosate. 

The current action is requesting application of glyphosate to a new variety of genetically altered 

corn developed by Monsanto (MON 87427 and MON87441). Monsanto indicated that MON 

87427 and MON87441 are tolerant to glyphosate via insertion of the CP4 EPSPS (5-

enolpyruvylshikimate-3-phosphate synthase) gene which, as indicated above, encodes for an 

EPSPS protein which is not inhibited by glyphosate. MON 87427 and MON 87441 were also 

genetically altered to utilize a promoter and intron combination to limit expression of CP4 

EPSPS in pollen microspore and tapetum cells. Therefore, little to no CP4 EPSPS protein is 

expressed in MON 87427 and MON87441 pollen, thus pollen from these events is susceptible to 

glyphosate. Glyphosate application to MON 87427 and MON87441 at early tassel development 

allows specific cross pollinations to be made without using the traditional methods to control self 

pollination. The petitioner indicated that the resulting hybrid corn seed has full vegetative and 

reproductive tolerance to glyphosate due to the dominance of the glyphosate-tolerant trait 

inherited from the male parent. A metabolism study has been previously been conducted with 

field corn genetically altered to express CP4 EPSPS with HED concluding that the residue of 

concern was glyphosate (see above). HED concludes that these data and decisions are 

translatable to MON 87427 and MON87441. 

Nature of the Residue – Livestock: The qualitative nature of the residue in livestock following 

dosing with glyphosate and AMPA is adequately understood. Studies with lactating goats and 

laying hens fed a mixture of glyphosate and AMPA indicate that the primary route of elimination 

was by excretion (urine and feces). HED determined that the terminal residue to be regulated in 

livestock is glyphosate (Memo, R. Perfetti, 19-Oct-1992; RED, R. Perfetti, 27-Oct-1992; Memo, 

R. Perfetti, 17-Mar-1994). 
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Since the Optimum GAT soybean and field corn metabolism studies resulted in significant 

residues of N-acetyl-glyphosate, DuPont submitted summaries of in vitro (rumen fluid, fertile hen

egg, and rat liver S9 supernatant) and in vivo (rat metabolism study) studies conducted with the 

N-acetyl-glyphosate metabolite and submitted goat and hen metabolism studies conducted with 

the N-acetyl-glyphosate metabolite. Based on these data and the glyphosate metabolism studies, 

HED concluded that the residues of concern in livestock following consumption of glyphosate 

and N-acetyl-glyphosate, for tolerance expression and risk assessment purposes, are glyphosate 

and N-acetyl-glyphosate (D346713, T. Bloem, 12-Mar-2008; D361315, T. Bloem, 14-Jan-2010). 

Based on these data and since MON 87427 and MON87441 field corn do not result in any

addition metabolites, HED concludes that the previous decisions concerning the residues of 

concern in livestock remain appropriate. 

Magnitude of the Residue – Field Corn: The petitioner submitted 10 field corn field trials 

conducted in the North American Free Trade Agreement (NAFTA) growing zones 5 (n=8) and 

5A (n=2). Each field trial consisted of two treated plots planted with inbred NK603 (tolerant to 

glyphosate vie insertion of the CP4 EPSPS gene) as the male pollen donator and either inbred 

MON 87427 or MON 87441 as the female parent (see Nature of the Residue section in the 

Executive Summary for a description of these varieties). Provided a revised Section B is 

submitted as described above, the employed application scenarios adequately mimic the proposed 

application scenario. The harvested field corn forage, stover, and grain samples were analyzed 

for residues of glyphosate and AMPA using an adequately-validated method (storage interval has 

also been validated). The maximum glyphosate residue in the treated field corn forage, grain and 

stover samples were 9.19 ppm, 0.80 ppm, and 30.85 ppm, respectively. HED has previously

determined that glyphosate residues do not concentrate in corn processed commodities 

(D216229, W. Cutchin, 21-Mar-1996).

Since the maximum glyphosate residue in field corn stover and grain is significantly less than the 

currently-established tolerances, revision of the stover and grain tolerances is unnecessary. 

However, the maximum glyphosate residue in field corn forage is greater than the currentlyestablished tolerance. HED entered the glyphosate field corn forage residue data into the 

Agency’s tolerance spreadsheet as specified by the Guidance for Setting Pesticide Tolerances 

Based on Field Trial Data; the resulting recommended tolerance is 13 ppm. Since the petitioner 

proposed field corn forage tolerance is for residue of glyphosate only, HED requests that a 

revised Section F be submitted proposing 13-ppm field corn forage tolerance for the combined 

residues of glyphosate and N-acetyl-glyphosate (expressed as glyphosate). 

HED notes that only 10 field trials were conducted and only in NAFTA growing zone 5. 

Therefore, the petitioner has not fulfilled the geographical requirements suggested in OPPTS 

860.1500 for a field corn registration. The petitioner noted that trials were only conducted in 

Zone 5 as this is the major hybrid seed corn production region in the U.S. Based on this and 

since residues in stover and grain were significantly lower than the currently-established 

tolerance and since the currently established 400 ppm nongrass animal feed and 300 ppm grass 

forage tolerances are significantly greater than the HED-recommend field corn forage tolerance, 

meaning that residues in field corn forage will not effect the currently-established ruminant 

tolerances, additional field trial data are not required. 
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Magnitude of the Residue - Livestock: The revised OPPTS 860.1000 Table 1 (J. Stokes; Jun2008) indicates that field corn forage (roughage), stover (roughage), grain (carbohydrate 

concentrate), and milled byproducts (carbohydrate concentrate) may fed to dairy/beef cattle and 

grain and milled byproducts may be feed to poultry and hogs. Since the current petition requires a 

revision to only the field corn forage tolerance (tolerance increased from 6.0 ppm to 13 ppm) and 

since the roughage portion of the beef/dairy cattle diet will be occupied by the currently established 

400 ppm nongrass animal feed and 300 ppm grass forage tolerances, HED concludes that the 

currently-established livestock tolerances remain appropriate. 

Nature/Magnitude of the Residue - Rotational Crops: Based on a previously-reviewed 

confined rotational crop studies (3.71 lb ae/acre; MRIDs 41543201 and 41543202, A. 

Abramovitch, 14-Oct-1992) which resulted in glyphosate residues of >0.01 ppm in barley grain 

only (0.018 ppm; 125-day plantback interval (PBI)) and the limit of quantitation (LOQ) for the 

tolerance enforcement method of 0.05 ppm, HED concluded that a 30-day PBI was appropriate 

for all nonlabeled crops (D200041, G. Kramer, 12-May-1994; field rotational crop study has not 

been submitted). HED notes that the rate employed in the confined rotational crop study was 

0.6x the proposed rate; however, based on the LOQ for the tolerance-enforcement method and 

since confined rotational crop study employed application to bare soil, HED concludes that the 

proposed 30-day PBI for all crops is acceptable. 

Analytical Enforcement Method: The field corn forage, stover, and grain samples collected 

from the crop field trials submitted in support of the current petition were analyzed for residues 

of glyphosate using a method similar to the current enforcement method. Based on this similarity

and since the field trial study resulted in acceptable recoveries, HED concludes that the current 

enforcement method is adequate to enforce the tolerances associated with the current petition. 

Recommendations: Provided the petitioner submits a revised Sections B and F (see below), HED 

concludes that the residue chemistry database supports an unconditional registration for the 

proposed application scenario. A human-health risk assessment will be prepared as a separate 

document. 

Summary of Residue Chemistries Deficiencies:

●Section B: HED requests that the supplemental labels be altered to indicate the following: (1) 

the minimum spray volume for ground and aerial application is >2 GPA; (2) postemergent 

directions should indicate that they apply to field corn up to the V8 crop stage and that a maximum 

of 2.3 lb ae/acre/season may be applied; and (3) PHI of 30 days for forage and 7 days for grain and 

stover.

●Section F: HED requests that a revised Section F be submitted proposing a 13-ppm field corn 

forage tolerance for the combined residues of glyphosate and N-acetyl-glyphosate (expressed as 

glyphosate). 
Glyphosate Summary of Analytical Chemistry and Residue Data DP#: 383931

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Background

Glyphosate is a nonselective Group 9 herbicide which disrupts the synthesis of the aromatic 

amino acids tyrosine, tryptophan, and phenylalanine through inhibition of EPSPS. Glyphosate is 

currently registered for pre- and post-emergence application to a variety of fruit, vegetable, and 

field crops. Tolerances are currently established for residues of glyphosate in/on various plant 

commodities (including field corn) at 0.2-400 ppm (40 CFR §180.364(a)) and for the combined 

residues of glyphosate and N-acetyl-glyphosate (expressed as glyphosate) in/on field corn, 

soybean, AGF, and livestock commodities at 0.1-310 ppm. The Glyphosate RED document was 

issued September 1993. A Registration Review Scoping document was completed in 2009 

(D362745, J. Langsdale et al., 3-Jun-2009). The chemical structure/nomenclature 

physicochemical properties of glyphosate are presented in Tables 1 and 2. 

Table 1: Glyphosate Nomenclature.

Compound P

O

OH

OH

N

H

HO

O

Common name Glyphosate (PC code 471300)

Company experimental name DPX-B2856

IUPAC/CAS name N-(phosphonomethyl)glycine

CAS registry number 1071-83-6

Table 2: Physicochemical Properties of Technical Grade Glyphosate.

Melting point 189.5 ± 0.5 °C

The Pesticide Manual, 13th Edition

pH 1.9 at 20 °C

Density 1.705 g/cm3at 20 °C

Water solubility 10.5 g/L at 20 °C

Solvent solubility

acetone 0.078 g/L

methanol 0.231 g/L

hexane 0.026 g/L

ethyl acetate 0.012 g/L

dichloromethane 0.233 g/L

n-octanol 0.020 g/L

propan-2-ol 0.020 g/L

toluene 0.036 g/L

European Commission: Glyphosate 

6511/VI/99-final, 1/21/02

Vapor pressure 1.31 x 10-2 mPa at 25 °C The Pesticide Manual, 13th Edition

Dissociation constant, pKa

0.8 (1st phosphoric), 2.3 

(carboxylate), 6.0 (2nd phosphoric), 

and 11.0 (amine)

Knuuttila. 1979 Acta Chem. Scand. B 

33:623-626

Octanol/water partition coefficient, Log(KOW) -3.2 (pH 2-5, 25 °C) European Commission: Glyphosate 

UV/visible absorption spectrum ε = 0.086 (295nm) 6511/VI/99-final, 1/21/02
Glyphosate Summary of Analytical Chemistry and Residue Data DP#: 383931

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860.1200 Directions for Use

The petitioner submitted proposed supplemental labels for Roundup WeatherMAX®(EPA Reg. 

No. 524-537) and Roundup Power MAX®(Reg. No. 524-549); both of these products are SC

formulations consisting of glyphosate as the potassium salt at 4.51 lb ae/gallon. The submitted 

supplemental labels indicate that the application scenarios are for use in research field trials and 

for seed production of corn hybrids using the RHSTM system. Table 3 is a summary of the 

proposed application scenarios. The proposed use directions are similar to that currently

registered with the exception of the tassel control instructions (V8-V13); maximum seasonal 

application rate is the same. HED requests that the supplemental labels be altered to indicate the 

following (a revised Section B is requested): (1) the minimum spray volume for ground and

aerial application is >2 GPA; (2) postemergent directions should indicate that they apply to field 

corn up to the V8 crop stage and that a maximum of 2.3 lb ae/acre/season may be applied; and 

(3) PHI of 30 days for forage and 7 days for grain and stover.

Table 3: Summary of Proposed Roundup Ready® Field Corn Application Scenario.

Formulation

(EPA Reg. No.) App. Timing App. Rate(lb ae/acre)

Max. App. Rate 

(lb ae/acre) Use Directions and Limitations

Roundup WeatherMAX®

(EPA Reg. No. 524-537; 

SC; 4.51 lb ae/gal)

Roundup Power MAX®

(EPA Reg. No. 524-549; 

SC; 4.51 lb ae/gal)

preplant, at planting, preemergence not specified 3.72

-For use in research field trails 

and for seed production of corn

hybrids using RHSTM. 

-Allow a minimum of 10 days 

between postemergent 

applications.

postemergence 0.56-0.78 not specified

tassel control (V8-V13 or 100 growing 

degree units; before flowering) 0.39-1.13 2.26

preharvest 0.78 not specified

postharvest not specified not specified

maximum seasonal application rate -- 5.98

860.1300 Nature of the Residue - Plants and Livestock

See Executive Summary.

860.1340 Residue Analytical Methods

The field corn forage, stover, and grain samples collected from the crop field trials submitted in 

support of the current petition were analyzed for residues of glyphosate and AMPA using an 

adequately-validated high-performance liquid chromatography (HPLC) equipped with a 

fluorescence detector method. Briefly, samples were extracted with chloroform:aqueous 0.1 N 

HCl (1:3). The aqueous layer was collected and applied to a Chelex® 100 column eluted with 6 

N HCl followed by an anion exchange resin also eluted with 6 N HCl. The sample was 

concentrated, dissolved in water, and analyzed. Based on the lowest level of method validation 

(LLMV), the LOQ is 0.05 ppm for each analyte/matrix. Apparent residues of glyphosate and 

AMPA were <LOQ in all control samples. Based on the acceptable recoveries and since 

interfering residues were <LOQ in controls, the employed analytical method is adequate for datacollection purposes. 

The data-collection method is similar to the current enforcement method (Memo, R. Perfetti, 

10/27/92). Based on this similarity and since acceptable recoveries were attained in the field 

trials, HED concludes that the current enforcement method is adequate to enforce the tolerances 

associated with the current petition. 
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860.1360 Food and Drug Administration (FDA) Multiresidue Methods (MRMs) Protocols

The Pestrak database (1990) indicates that recoveries are not likely for glyphosate under FDA 

Multiresidue Methods. No further data regarding multiresidue methods are required for this 

proposed use. 

860.1380 Storage Stability

The maximum interval from collection to extraction for the forage, stover, and grain samples was

284 days (9.5 months). Previously submitted data indicate that glyphosate is stable for 31 

months in/on fortified and frozen corn, sorghum straw, clover, tomato, and soybean forage; 

residues of AMPA fluctuated from 50-99% in the same time period (D206278, C. Eiden, 17-

Nov-1994). Since AMPA is not a residue of concern in plants (Memo, R. Perfetti, 17-Mar1994), HED concludes that the available storage stability data are sufficient to validate the 

residue data submitted in support of the current petition. 

860.1480 Meat, Milk, Poultry, and Eggs

The revised OPPTS 860.1000 Table 1 (J. Stokes; Jun-2008) indicates that field corn forage 

(roughage), stover (roughage), grain (carbohydrate concentrate), and milled byproducts 

(carbohydrate concentrate) may fed to dairy/beef cattle and grain and milled byproducts may be 

feed to poultry and hogs. Since the current petition requires a revision to only the field corn forage 

tolerance (tolerance increased from 6.0 ppm to 13 ppm) and since the roughage portion of the 

beef/dairy cattle diet will be occupied by the currently established 400 ppm nongrass animal feed 

and 300 ppm grass forage tolerances, HED concludes that the currently-established livestock 

tolerances remain appropriate. 

860.1500 Crop Field Trials

47982201.der.doc

The petitioner submitted 10 field corn field trials conducted in the NAFTA growing zones 5 

(n=8) and 5A (n=2). Each field trial consisted of two treated plots planted with inbred NK603 

(tolerant to glyphosate vie insertion of the CP4 EPSPS gene) as the male pollen donator and 

either inbred MON 87427 or MON 87441 as the female parent (see Nature of the Residue section 

in the Executive Summary for a description of these varieties). Table 4 is a summary of the 

employed application scenarios; provided a revised Section B is submitted as described above, 

the employed application scenarios adequately mimic the proposed application scenario. All 

applications were broadcast sprays made with Roundup WeatherMAX®(EPA Reg. No. 524-537; 

water-soluble concentrate formulation of glyphosate formulated as the potassium salt (4.5 lb 

ae/gal; 540 g ae/l)) and included (NH4)2SO4 and a nonionic surfactant (NIS). The harvested field 

corn forage, stover, and grain samples were analyzed for residues of glyphosate and AMPA 

(aminomethyl phosphonic acid) using an adequately-validated method (storage interval has also 

been validated). Table 5 is a summary of the residue data. In general, residues were higher 

under the treatment 2 application scenario as compared to the treatment 3 application scenario 

(only slightly higher in grain). 
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Conclusions: Tolerances for the combined residues of glyphosate and N-acetyl-glyphosate 

(expressed as glyphosate) in/on field corn forage, stover, and grain are currently established at 

6.0 ppm, 100 ppm, and 5.0 ppm, respectively (180.364(a)(2)). HED notes that the tolerance 

expression includes residues of N-acetyl-glyphosate due to the introduction the Optimum

GAT field corn variety (see Nature of the Residue Section in the Executive Summary for a 

description of this variety). 

Since the maximum glyphosate residue in field corn stover (30.85 ppm) and grain (0.80 ppm) is 

significantly less than the currently-established tolerances, revision of the stover and grain 

tolerances is unnecessary. However, the maximum glyphosate residue in field corn forage (9.19 

ppm) is greater than the currently-established tolerance. HED entered the glyphosate field corn 

forage residue data from the treatment 2 scenario (resulted in higher residues) into the Agency’s 

tolerance spreadsheet as specified by the Guidance for Setting Pesticide Tolerances Based on 

Field Trial Data (see attachment 2); the resulting recommended tolerance is 13 ppm (see 

Attachment 3). Since the petitioner proposed field corn forage tolerance is for residue of 

glyphosate only, HED requests that a revised Section F be submitted proposing a 13-ppm field 

corn forage tolerance for the combined residues of glyphosate and N-acetyl-glyphosate. 

HED notes that only 10 field trials were conducted and only in NAFTA growing zone 5. 

Therefore, the petitioner has not fulfilled the geographical requirements suggested in OPPTS 

860.1500 for a field corn registration (zones 1 (n=1), 2 (n=2), 5 (n=17), and 6 (n=1)). The 

petitioner noted that trials were only conducted in Zone 5 as this is the major hybrid seed corn 

production region in the U.S. Based on this and since residues in stover and grain were 

significantly lower than the currently-established tolerance and since the currently established 

400 ppm nongrass animal feed and 300 ppm grass forage tolerances are significantly greater than 

the HED-recommend field corn forage tolerance, meaning that residues in field corn forage will 

not affect the currently-established ruminant tolerances, additional field trial data are not 

required.

Table 4: Summary of Application Scenarios.

lb ae/acre (kg ae/ha)

premeergence V3-V4 V7-V8 V9-V10 V12-V13 late dent total

treatment 2 0.76-0.80

(0.85-0.90)

1.09-1.15

(1.22-1.29)

1.09-1.15

(1.22-1.29)

1.0-1.17

(1.20-1.31)

1.12-1.15

(1.26-1.29)

0.77-0.81

(0.86-0.91)

6.00-6.15

(6.73-6.89)

treatment 3 1.54-1.58

(1.73-1.77)

1.12-1.16

(1.26-1.30)

1.10-1.15

(1.23-1.29)

0.77-0.80

(0.86-0.90)

0.77-0.80

(0.86-0.90)

0.77-0.81

(0.86-0.91)

6.14-6.23

(6.86-6.98)

retreatment interval 

(RTI; days) -- 16-35 9-25 6-11 4-11 55-88 --

Table 5: Summary of Glyphosate and AMPA Residues.

Analyte Commodity Treatment Residues (ppm)

Range Mean

glyphosate

forage 2 2.59-9.19 5.73

3 1.95-6.88 4.34

stover

2 11.08-30.85 18.05

3 4.26-21.47 12.42

grain (collected 1 day prior to 

the final application)

2 0.19-0.77 0.40

3 0.15-0.45 0.26

grain (collected 7 days after the 

final application)

2 0.19-0.80 0.46

3 0.16-0.74 0.34
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Table 5: Summary of Glyphosate and AMPA Residues.

Analyte Commodity Treatment Residues (ppm)

Range Mean

AMPA

forage 2 0.07-0.25 0.15

3 0.07-0.19 0.12

stover

2 0.14-0.41 0.28

3 0.07-0.34 0.21

grain (collected 1 day prior to 

the final application)

2 0.05-0.11 0.08

3 <0.05-0.08 0.06

grain (collected 7 days after the 

final application)

2 0.06-0.10 0.08

3 <0.05-0.08 0.06

860.1520 Processed Food and Feed

HED has previously determined that glyphosate residues do not concentrate in corn processed 

commodities (D216229, W. Cutchin, 21-Mar-1996).

860.1850 & 860.1900 Confined and Field Accumulation in Rotational Crops

Based on a previously-reviewed confined rotational crop studies (3.71 lb ae/acre; MRIDs 

41543201 and 41543202, A. Abramovitch, 14-Oct-1992) which resulted in glyphosate residues 

of >0.01 ppm in barley grain only (0.018 ppm; 125-day PBI) and the LOQ for the tolerance 

enforcement method of 0.05 ppm, HED concluded that a 30-day PBI was appropriate for all 

nonlabeled crops (D200041, G. Kramer, 12-May-1994; field rotational crop study has not been 

submitted). HED notes that the rate employed in the confined rotational crop study was 0.6x the 

proposed rate; however, based on the LOQ for the tolerance-enforcement method and since 

confined rotational crop study employed application to bare soil, HED concludes that the a 30-

day PBI for all nonlabeled crops is acceptable. 

860.1550 Proposed Tolerances

Table 6 is a summary the proposed and HED-recommended tolerances for the combined residues 

of glyphosate and N-acetyl-glyphosate (expressed as glyphosate); a revised Section F is 

requested. There are no Mexican, Canadian, or Codex field corn forage maximum residue limits 

(MRLs) but there is a Canadian MRL in/on “corn” of 3.0 ppm and a Codex MRLs in/on “maize”

of 5 ppm which could be applied to any corn commodity (see Attachment 1). Regardless, since 

the residues of concern differ, harmonization is not possible. 

Table 6. Tolerance Summary.

Commodity Proposed 

Tolerance (ppm)

HED-Recommended 

Tolerance (ppm) Comments

corn, field, 

forage 13 13

The petitioner proposed tolerance is for residues of glyphosate 

only while the HED-recommended tolerance is for the combined 

residues of glyphosate and N-acetyl glyphosate; a revised 

Section F is requested.

Attachment 1 - International Residue Limit Status sheet

Attachment 2 - Chemical Name and Structure Table

Attachment 3 - Tolerance Spreadsheet Summary

RDI: RAB1 Chemists (8-Dec-2010)

T. Bloem:S10945:Potomac Yard 1:703-605-0217:7509P:RAB1
Glyphosate Summary of Analytical Chemistry and Residue Data DP#: 383931

page 11 of 13

Attachment 1 – Glyphosate International Residue Limit Status Sheet

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex

40 CFR 180.364(a)(2): glyphosate 

and N-acetyl-glyphosate

N-(phosphonomethyl)

glycine, including the 

metabolite aminomethyl

phosphonic acid

--

glyphosate

Tolerance (ppm) /Maximum Residue Limit (mg/kg)

Commodity1 US Canada Mexico2 Codex

Corn, field, forage 13 3.0 (corn) -- 5 (maize)

Completed M. Negussie; 12/01/2010

1

 Includes only commodities of interest for this action. Tolerance values should be the HED recommendations and 

not those proposed by the applicant.

2

 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.
Glyphosate Summary of Analytical Chemistry and Residue Data DP#: 383931

page 12 of 13

Attachment 2 - Chemical Structures

Compound Structure

Glyphosate

N-(phosphonomethyl)glycine

P

O

OH

OH

N

H

HO

O

N-acetyl-glyphosate

N-acetyl-N-(phosphonomethyl)glycine

AMPA

(aminomethyl)phosphonic acid P

O

OH

OH

H2N

N-acetyl-AMPA

[(acetylamino)methyl]phosphonic acid P

O

OH

OH

N

H

H3C

O

P

O

OH

OH

N

HO

O

H3C O
Glyphosate Summary of Analytical Chemistry and Residue Data DP#: 383931

page 13 of 13

Attachment 3: Tolerance Spreadsheet Summary

Regulator: EPA

Chemical: glyphosate

Crop: field corn forage

PHI:

App. Rate:

Submitter:

n: 22

min: 2.59

max: 9.19

median: 5.37

average: 5.73

95th Percentile 99th Percentile 99.9th Percentile

9.0 11 12

(11) (13) (--)

10 13 17

(13) (18) (--)

15

12

30

0.9669

p-value > 0.05 : Do not reject lognormality assumption

Approximate 

Shapiro-Francia 

Normality Test 

EU Method I

Normal

UCLMedian95th

95/99 Rule

EU Method II

Distribution-Free

Mean+3SD